Polyphenylene ether or modified phenylene ether resins are high performance engineering thermoplastics that have found extensive uses in a wide variety of manufacturing areas including automotive applications, e.g., dashboards, electrical connectors, filler panels, grilles, wheel covers and exterior body parts. In such automotive environments, there is a need for developing polyphenylene ether resins that demonstrate various properties including high impact strength, and resistance to solvents and thermal exposure.
A number of investigations have been conducted with respect to incorporating rubbery polymers into polyphenylene ether resins to improve their impact strengths. By way of illustration, these include Cizek, U.S. Pat. No. 3,383,435, who used styrene resins combined with blended or grafted diene rubbers; Katchman and Lee, U.S. Pat. No. 4,128,602, who used styrene grafted diene rubbers; Cooper et al., U.S. Pat. No. 4,152,316, who used styrene grafted ethylene propylene diene (EPDM) terpolymer rubbers, and the like. Solvent resistance and thermal aging resistance are not optimum for special uses, although impact strengths are excellent.
Sulfonated EPDM has also been blended with polyphenylene ether resins free of styrene resins, e.g., European Patent Application No. 168,652, published Jan. 22, 1986, and, including styrene resin, e.g., PCT Invention Application 85/1056, published Mar. 14, 1985, the impact strength is improved, but again, solvent resistance is less than optimum.
In Haaf, U.S. Pat. No. 4,322,507, styrene-ethylene-butylene block copolymers are disclosed as impact modifiers in polystyrene-free blends of polyphenylene ether to improve thermal resistance, solvent resistance, and enhance resistance to delamination. Impact strength, while high, could be improved; and resistance to delamination, while good, could also be improved.
It has now been discovered that by functionalizing the polyphenylene ether and the rubber and melt reacting such functional groups, better compositions in terms of impact strength, resistance to delamination and surprisingly improved solvent resistance can be obtained.
Galluci et al., U.S. patent application Ser. No. 901,434, filed Aug. 28, 1986, disclose polyphenylene ether resins functionalized by using a modifier comprising at least one alpha, beta-unsaturated carboxylic acid, or derivative, or a malimide, to improve processability and resistance to oxidative degradation.
It has also been proposed to graft fumaric acid onto polyphenylene ether resin in an extrusion process before blending with poly(1,4-butylene terephthalate) and PPO to obtain improved impact strength and solvent resistance. Neither technique uses functionalized rubber however.
In the prior disclosures of Olivier, U.S. patent application, Ser. No. 690,613, filed Jan. 11, 1985, now abandoned, Pratt et al., U.S. patent application Ser. No. 004,089, filed Jan. 16, 1987, now abandoned, and McHale et al., U.S. patent application Ser. No. 027,707, filed Mar. 19, 1987, glycidyl methacrylate (GMA) grafted EPDM rubbers are described as impact modifiers for polyester resins. There is no hint or suggestion, however, in such prior disclosures that such functionalized rubbery impact modifiers could be used with functionalized polyphenylene ether resins to produce interpolymers, e.g., grafted copolymers having improved physical properties.
It has now been unexpectedly discovered that glycidyl methacrylate grafted natural and synthetic rubbers, e.g., EPDM (EPDM-g-GMA) impact modifiers can be incorporated into functionalized polyphenylene ether resins, e.g., fumaric acid functionalized poly(2,6-dimethyl-1,4-phenylene ether resins), to provide compositions of high impact strength, improved solvent resistance and overall better physical properties. Delamination is unexpectedly low while solvent resistance is surprisingly high.